Mac's Service Shop: Customer Cues
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In 1958 when this "Customer Cues" installment of John T. Frye's "Mac's Service Shop" series of technodramas in Radio & TV News magazine, color television was a relatively new phenomenon. The first commercially sold color TV set - the Admiral C1617A - went on sale at the very end of 1953. The NTSC (National Television System Committee) approved the first standardized specification for a composite color television composite signal (color, gray scale, audio, brightness, synchronization) earlier that year. It allowed the same signal to work with both black and white (B&W) and color receivers. A lot of research went into making sure the viewing public was happy with their sets, using polls, hands-on instruction and publications on how to properly adjust tuning and picture controls, plus tips on installing outdoor antennas and running the twin lead transmission cable down to the set. Of course the proper way to fiddle with the built-in "rabbit ears" antenna was covered as well. I don't think any official pamphlets included mashing tinfoil onto the rabbit ears in complex patterns as many people did - truth is, it must have worked in some cases. In the story, Mac schools Barney on the situation. Mac's Service Shop: Customer Cues
It was October and the landscape was aflame with "Living Color." The morning was a perfect setting for the fall beauty. Barney stood for a moment before entering the shop looking at the morning-glory blue of the sky overhead, breathing deeply of the cool clean air rising from the dew-wet grass, and noting appreciatively the way the sun splashed its warm light on the red, green, purple, and russet leaves of the trees across the street. He heaved a little sigh and turned and entered the shop. "Hey, boss," he greeted Mac, his employer, "Nature really has the color control turned full on today." "Yep," Mac said as he flipped a little a.c:d.c. chassis over on its back; "and did you notice that she always has the hue control set just right?" "That's more than I can say for a lot of our customers," Barney remarked as he took his shop coat from the closet. "Most of them can't even tune a little radio like the one you're working on." "Why do you say that?" Mac asked with a quizzical look. "Cause it's true. You know what a sloppy job of tuning ordinary black-and-white TV sets most people do." "No I don't," Mac demurred. "People usually have a little trouble right at the beginning, but it's been my experience that most of them learn to do a pretty creditable job of adjusting the set, especially if the person who installs it does his job and gives them adequate instructions. They usually do not have the foggiest notion of what turning each knob actually does and quite often they cannot tell someone else how to adjust the receiver, but still and all most people manage to adjust their own sets so as to produce a good picture. They just keep twisting the knobs and watching the picture and listening to the sound until they stumble on a procedure that gets results. Eventually they act almost instinctively to correct any picture fault that shows up." "One man's opinion!" Barney grunted. "It's more than that," Mac insisted. "Recently a group at Iowa State College made a study for the FCC of just how well the average TV viewer adjusted his receiver and they were surprised to learn he does a darned good job of it. They found out he was just as capable of distinguishing between a good and bad picture as were the engineers- something few technicians will ever believe -and the great majority of viewers could set the controls to get the best possible picture." "Maybe so," Barney admitted grudgingly; "but they certainly talk a lot of gibberish. They call a ghost a 'shadow,' confuse the contrast and brightness controls, and talk about the picture as being 'soft,' 'hard,' 'smooth,' 'grainy,' and goodness knows what all else." "No law says they have to use our technical vocabulary. Keep that in mind. Instead of laughing at their terms, try hard to understand exactly what they mean. And along the same line, when you're making a house call, always try to maneuver the set owner into turning his receiver on and adjusting it if you can." "Why?" "For several reasons. For one thing, that relieves you of the necessity for hunting out the right controls. We know there's no reason in the world why a technician should have in mind the exact location of every control on hundreds of different models of TV receivers, but the customer can't grasp this. When he sees you fumbling around for the knob that turns the set on, he jumps to the conclusion you don't know much about his particular set." "I'll buy that." "Also, if he IS misadjusting his receiver, you have a chance to catch him at it. Of course you never tell him he has been doing something wrong, especially if his wife's in the room. You simply do it right and make sure that he sees how you do it. I am 'agin' the tendency of many technicians to regard their customers as being one cut above complete idiots. I know this makes for a lot of very funny smart aleck talk among technicians - telling what stupid boo -boo's their customers pull - but it is a dangerous pitfall for a technician. He wants the respect of his customers, but it's pretty hard to get respect unless you give it. And it's a cheap feeling of superiority you get from anointing yourself with the ego -salve of narrow technical knowledge. Insist on doing that and you are laying yourself wide open to being considered a moron by the doctor, lawyer, chemist, jeweler, automobile mechanic, and hundreds of other trades and professions." "Don't worry about me," Barney said. "Now and then I get a little impatient because a customer has some wacky electronic idea or seems a little slow about grasping what I'm trying to tell him; but I don't pop off about what I think. Not to change the subject, how are you making out with that little receiver. I put in an hour on it last evening without finding out what was producing that funny squelch effect." Before answering, Mac tuned the little receiver across the band. There was absolute silence between stations with no trace of normal hiss; but when strong stations were tuned in, the reception seemed normal. "What all did you try?" Mac asked his assistant. "Well, a gassy tube will often cause that; so I changed the mixer, i.f. tube, and the combination detector - a.v.c first -audio tube. No dice. Then I decided maybe the audio coupling capacitor was open until a strong signal temporarily bridged the break, but paralleling it with a good capacitor made no difference. Next I checked the a.v.c. resistors to see if any were open or had seriously changed value. All were OK. By then it was time to knock off." "And if I know you, you dropped the solder gun at the first stroke of the clock," Mac growled. "Let's get out the signal tracer." The signal was easily traced through the mixer, the i.f. amplifier, and right up to the secondary of the second i.f. transformer; but there it disappeared. That is, it disappeared until a strong signal was tuned in. When a weak signal was being received, the signal was present across the transformer primary, but it could not be picked up across the secondary. Mac laid aside the signal tracer probe and flipped on the v.t.v.m. Carefully he checked the voltages at the pins of the 12AT6. When the probe was touched to the diode detector plate, a small positive voltage was noticed. Mac tried another tube without changing the condition. Then he picked up the diagonal cutters and cut the lead going from the i.f. transformer secondary to the diode plate. The voltage appearing on the cut transformer lead became still more positive. Quickly and deftly Mac cut loose the leads of the small slug -tuned transformer and lifted it out of the chassis. He switched to the ohmmeter and measured the resistance appearing between the two windings. An easily measured resistance of several thousand ohms was indicated. It took Mac only a few minutes to get a duplicate transformer from stock and install it in the receiver. Barney always enjoyed watching his boss work. The man's big hands moved as confidently and surely as those of a surgeon and there was absolutely no waste motion. The wires were connected and neatly soldered so that the new solder connections could not be detected from those done at the factory. As soon as the set was turned on, it was apparent the trouble had been found and eliminated. The receiver had lost its unique squelch effect. Weak and strong stations both were tuned in smoothly. Mac carefully aligned the whole i.f. system and touched up the oscillator and r.f. trimmers. The receiver worked perfectly; so he wiped out the plastic case and put the chassis into it. "Oh don't look so smug!" Barney erupted. "How did the i.f. transformer produce that odd effect?" "You should be able to figure it out. What would be the effect of that leakage between windings?" "I suppose the 'B-plus' on the primary would put a positive potential on the diode plate." "Right. And that would make the diode conduct and virtually short-circuit the secondary until enough signal appeared across the secondary to override the positive bias." "What caused the leakage?" "I think it is a little moisture that gets into the capacitors molded into the base of the transformer. At least I have been able to cure it temporarily by baking the transformer for a few hours under a heat lamp." "So-o-o-o! You knew all along what was wrong. How come you went through all that rigamarole with the signal tracer and the v.t.v.m.?" "Because I wasn't sure. Actually, this condition is more often brought on by a defective tube than it is by an i.f. transformer; but during the hot summer months I noticed a small rash of this particular kind of transformer trouble. When it happens to an input transformer, the symptom is more likely to be low gain and an intermittent crackling noise. I used the signal tracer and the v.t.v.m. because I always try to follow a logical procedure in running down an unusual symptom." "We surely are doing a lot of work on these little receivers," Barney said. "I believe people are listening to radio a lot more than they did a year or so ago." "That's right, but it's a specialized kind of listening. The kids listen to a favorite disc jockey; the woman listens to morning programs in the kitchen; Pop listens to the ball games. And incidentally, it does not hurt a bit to inquire casually what stations are favorites with the family when the set is brought in. Since that new station has opened up in Garden City on 1600 kc., you want to be sure and see that the receiver will tune up to it. By the same token the station on 560 carries the ball game and you want to be certain it can be picked up. A lot of people listen to a religious station around 1110 kc. You can make them happy by peaking the set up on that frequency. The same goes for other pet stations. Ideally, of course, the receiver should be made to track perfectly clear across the band; but practically, you can usually make a noticeable improvement on a particular frequency by careful peaking of the r.f. trimmer at that frequency after you have done the best you can to get good tracking." "Gotcha, chief!" agreed Barney.
Posted April 17, 2024 Mac's Radio Service Shop Episodes on RF Cafe This series of instructive technodrama™ stories was the brainchild of none other than John T. Frye, creator of the Carl and Jerry series that ran in Popular Electronics for many years. "Mac's Radio Service Shop" began life in April 1948 in Radio News magazine (which later became Radio & Television News, then Electronics World), and changed its name to simply "Mac's Service Shop" until the final episode was published in a 1977 Popular Electronics magazine. "Mac" is electronics repair shop owner Mac McGregor, and Barney Jameson his his eager, if not somewhat naive, technician assistant. "Lessons" are taught in story format with dialogs between Mac and Barney.
Color and Monochrome (B&W) Television Articles
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